Pediatric organ transplantation and risk of premalignant and malignant tumors in Sweden

Increased cancer risks are well documented in adult organ transplant recipients. However, the spectrum of malignancies and risk in the pediatric organ transplant population are less well described. We identified all solid organ transplanted patients aged <18 in Sweden between 1970-2007 (n = 536) in the National Patient Register and linked to the Cancer Register. Nationwide rates were used to calculate standardized incidence rate ratios and 95% CI estimating the association between transplant and cancer during maximum 36 years of follow-up. Nearly 7% of pediatric solid organ transplant recipients developed a premalignant or malignant tumor during follow-up. Transplantation was associated with an increased risk of any cancer (n = 24, SIR = 12.5, 95% CI: 8.0-18.6): non-Hodgkin lymphoma (NHL) (n = 13, SIR = 127, 95% CI: 68-217), renal cell (n = 3, SIR = 105, 95% CI: 22-307), vulva/vagina (n = 3, SIR = 665, 95% CI: 137-1934) and nonmelanoma skin cancers (n = 2, SIR = 64.7, 95% CI: 7.8-233.8). NHL typically appeared during childhood, while other tumors were diagnosed during adulthood. Apart from short-term attention toward the potential occurrence of NHL, our results suggest cancer surveillance into adulthood with special attention to skin, kidneys and the female genitalia.